1. Field of the Invention
The present invention relates generally to a mine emergency communication cable and method for use and more particularly to a cable made of a lightweight rope having a plurality of noninsulated electrically conducting wires intertwined in the rope. One or more insulated electrically conducting wires can be intertwined in the rope.
2. Description of the Prior Art
Current techniques for effecting the rescue of miners trapped or injured underground involve sending a rescue team from a surface location or some other safe area to aid the trapped or injured miners. Frequently, the members of the rescue team pull a heavy two core insulated cable into the mine. This heavy cable connects the rescue team, via a sound powered microphone, to a fresh air base. Pulling this cable into the mine expends a considerable amount of the rescue team's energy. Additionally, if the rescue team encounters an obstruction in the mine, the heavy cable must be reeled in while the rescue team backtracks in order to prevent entanglement or snagging of the heavy cable.
Gallagher Electronics, Ltd., a New Zealand Corporation, has developed and marketed a lightweight rope comprised of synthetic fibers which includes a plurality of noninsulated stainless steel and copper conducting wires intertwined with the synthetic fibers. This lightweight rope is used as an electric fence for restraining cattle or sheep. A similar product containing aluminum wire is manufactured and in use in Canada. To the inventor's knowledge, neither of these products have been used in communication applications.
A medium frequency radio communication system which utilized transceivers coupled to the existing mine wiring network was described by L. G. Stolarczyk and R. L. Chufo in a paper entitled System Design and Performance of an MF Radio Communication System For Underground Mining, (September 1981). As discussed in that paper, early theoretical work by D. A. Hill and J. R. Wait in Excitation of Monofilar and Bifilar Modes on a Transmission Line in a Circular Tunnel, Journal of Applied Physics, Vol. 45, No. 8 (August 1974), described the existence of low loss signal propagation modes that exist in underground tunnels containing conductors.